Click-back-to-window crashing problem
Don't worry guys. I figured out the reason behind the problem and fixed it.

The story behind it:

One day, I went looking for new art software (because I've been using Inkscape a lot; i still do, honestly), and I came across Medibang. When I installed it, it didn't look all that interesting to me, so I uninstalled it immediately. In the middle of that, though, came a message that said whether or not I wanted to get rid of "MdpThumb64.dll", and if I chose "No", it would cause no harm. So I clicked "No" on that message and went on with my day. 

After that, every other time I went to get on the computer, it would always take a while to load up everything , and I was thinking that the .dll file was the problem, so I deleted it and then felt instant regret doing that. I then went to a DLL-downloading website, and downloaded the .dll from there. I never should've trusted them, because that's when the chaos finally ensued.

I went to Blender, clicked off and on the window again, and it closed itself (which was the main problem here). I could only assume the fake .dll file was behind all this, so I did a System Restore (in which the restore point was all the way back in January of 2019), tried the click-on-and-off thing again, and nothing happened. It never closed on itself after that, therefore I finally solved the problem. 

I guess it turns out that there was no "MdpThumb" DLL file on Windows to begin with. (hehe)